23
Function (see also Fig. 451_040 on page 24)
At first, the gas and oil spray mixture admitted into the rocker
cover flows into a relatively large hollow chamber, where the first
oil droplets deposit on the walls. The gas then passes through a
fine oil separator.
The fine oil separator operates on the centrifugal force principle
and employs a so-called axial cyclone (*Polyswirl
TM
).
The separator comprises four permanently open swirls and six
packs of up to nine swirls, which can be activated and deactivated
according to the flow rate.
The six packs are activated and deactivated by locking springs with
different spring characteristics.
The fine oil separator is opened by the flow of blow-by gases
(which is dependent on engine speed) and closed by the spring
force of the locking springs.
The separated oil coming from the rocker cover and the fine oil
separator is recirculated continuously into the oil pan below the
engine oil level via the oil return line.
In the extreme event of icing or malfunctioning, a pressure relief
valve in the rocker cover (PCV combi valve) prevents excessively
high pressure from damaging the engine. To avoid drawing oil
from the oil pan into the intake in such a condition, another non-
return valve closes. This valve is integrated in the upper part of the
oil pan.
The cleaned blow-by gas is now directed to the engine for combus-
tion. For this purpose, the gas passes through the single-stage
pressure-regulating valve. Depending upon the compression ratio
in the intake manifold, they then flow through the non-return
valves into the intake manifold downstream of the throttle valve
or upstream of the exhaust turbocharger turbine.
The pressure-regulating valve is integrated in the rocker cover,
where there is sufficient space to allow a larger valve of single-
stage design. The non-return valves (to the intake manifold or to
the supercharger side) are optimised for pressure differential and,
together with the pressure-regulating valve, produce the required
partial vacuum in the crankcase.
451_035
SwirlCleaned blow-by gas
Separated oil
Blow-by gas inlet
(raw gas)
Fine oil separator
Pack of swirls (9 per pack)
Locking springs with differ-
ent spring rates
Permanently open swirls
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